Pedicle screw system for osteosynthesis

• US 5,782,833 A
• Filed: 12/20/1996
• Issued: 07/21/1998
• Est. Priority Date: 12/20/1996
• Status: Expired due to Term

• Current Assignee: Thomas T. Haider
• Original Assignee: Thomas T. Haider
• Inventors: Haider, Thomas T.
• Primary Examiner(s): Buiz, Michael
• Assistant Examiner(s): REIP, DAVID OWEN
• Application Number:
  US08/771,133
• Time in Patent Office: 578 Days
• Field of Search: 606/60, 606/61, 606/72, 606/73
• US Class Current: 606/266
• CPC Class Codes: A61B 17/7032 Screws or hooks with U-shaped head or back through which longitudinal rods pass
• CPC Class Codes: A61B 17/7037 wherein pivoting is blocked when the rod is clamped
• CPC Class Codes: Y10T 403/32311 Ball and socket
• CPC Class Codes: Y10T 403/49 Member deformed in situ

Abstract

A pedicle screw assembly 10 for use with a rod 11 for the immobilization of bone segments. The assembly is composed of a screw 12, a polyaxial housing 20, a washer 34, a set screw 48, and a cup-shaped cap 40. When the screw is placed inside the polyaxial housing 20, the head of the screw 18 comes into contact with a middle section of the polyaxial housing 20 and is secured into the bone so that the polyaxial housing is pivotable with three degrees of freedom. The housing includes a pair of upstanding posts 30 with interior threads. A washer 34 is inserted between the head of the screw 12 and the rod. A cap 40, having a bottom, with a pair of posts accommodating openings 43 and a lateral cross connector 44, is placed over the posts 30 so that the cross connection 44 engages the rod. A set screw 48 is threaded into the housing posts to secure the rod within the housing.

Claims

1. A pedicle screw assembly for use in conjunction with a rod for immobilizing bone segments comprising:

a screw having a cylindrical threaded shaft and a head, the head having a larger diameter than the shaft with a generally spherically convex bottom section jointed to the shaft and a top section defining a wrench engaging surface so that the screw may be rotatably inserted into a bone segment;

a polyaxial housing having a top, middle and bottom section, with a stepped axial bore therethrough, the diameter of the bore in the bottom section being larger than the diameter of the cylindrical shaft and smaller than the diameter of the screw head, the diameter of the bore in the top section of the housing having a diameter greater than the diameter of the head of the screw, the middle section of the housing having a generally spherically concave inside surface extending between the bore diameters in the top and bottom sections whereby the cylindrical shaft of the screw may pass through the housing while the head is retained in the middle section of the housing, the top section of the housing defining a pair of spaced upstanding posts with a threaded inside surface, the posts defining a slot therebetween for receiving the rod;

a cup-shaped cap adapted to be inserted over the top section of the housing after the rod has been inserted through the housing slot, the cap having a bottom defining a pair of spaced openings for receiving the posts and a cross-connector spanning the lateral width of the inside surface of the cap between the openings, the cross-connector having a lower concave surface for engaging the rod and an upper surface;

a set screw having a head with a wrench engaging surface, a threaded shaft adapted to be threadably received in the threaded surface of the housing and a free end for engaging the upper surface of the cross-connector of the cap to secure the rod between the cross-connector and the screw head; and

a washer with a top and bottom, the bottom of the washer including a concave surface adapted to engage the head of the screw, the top of the washer having a concave recess adapted to engage the rod, the washer being located within the polyaxial housing between the head of the screw and the rod.

2. The pedicle screw assembly of claim 1 wherein the screw, housing, cap, and set screw are made of titanium.

3. A pedicle screw assembly for use in conjunction with a rod for immobilizing bone segments comprising:

a screw having a cylindrical threaded shaft and a head having a larger diameter than the shaft with a generally spherically convex bottom section jointed to the shaft and a top section having a generally spherical convex surface defining a wrench engaging surface therein so that the screw may be rotatably inserted into a bone segment;

a polyaxial housing having a top, middle and bottom section, with a stepped axial bore therethrough, the diameter of the bore in the bottom section being larger than the diameter of the cylindrical shaft and smaller than the diameter of the screw head, the diameter of the bore in the top section of the housing having a diameter greater than the diameter of the head of the screw, the middle section of the housing having a generally spherically concave inside surface extending between the bore diameters in the top and bottom sections whereby the cylindrical shaft of the screw may pass through the housing while the head is retained in the middle section of the housing, the top section of the housing defining a pair of spaced upstanding posts with a threaded inside surface, the posts defining a slot therebetween for receiving the rod;

a washer adapted to be inserted into the polyaxial housing after insertion of the screw through the polyaxial housing, the washer having a top and bottom, the bottom of the washer having a generally concave spherical shape being adapted to receive the head of the screw, the rod being inserted through the housing slot coming into contact with the top of the washer, the top of the washer having a longitudinal saddle shaped recess being adapted to receive the rod;

a cup-shaped cap adapted to be inserted over the top section of the housing after the washer is in place between the head of the screw and the rod, the cap having a bottom defining a pair of spaced openings for receiving the posts and a cross-connector spanning the lateral width of the inside surface of the cap between the openings, the cross-connector having a lower generally cylindrical concave surface for engaging the rod and an upper surface; and

a set screw having a head with a wrench engaging surface, a threaded shaft adapted to be threadably received in the threaded surface of the housing and a free end for engaging the upper surface of the cross-connector of the cap to secure the rod between the cross-connector and the screw head.

4. A pedicle screw assembly for use in conjunction with a rod for immobilizing bone segments comprising:

a screw having a threaded shaft and a heads the head having a larger diameter than the shaft and defining a generally spherically convex bottom and top surface and a wrench engaging socket in the top surface;

a polyaxial housing having a top, middle and bottom section, with a stepped axial bore therethrough, the diameter of the bore in the bottom section being larger than the diameter of the threaded shaft of the screw and smaller than the diameter of the screw head, the diameter of the bore in the top section of the housing having a diameter greater than the diameter of the head of the screw, the middle section of the housing defining a generally spherically concave interior surface extending between the bore diameters in the top and bottom sections whereby the cylindrical shaft of the screw may pass through the housing while the head is retained in the middle section of the housing, the top section of the housing defining at least two spaced upstanding posts with a threaded inside surface, and a slot therebetween for receiving the rod, the housing being arranged to pivot and rotate relative to the head of the screw to accommodate bends in the rod;

a cup-shaped cap adapted to be inserted over the top section of the housing after the rod has been inserted through the housing slot, the cap having a bottom defining at least two spaced openings for receiving the posts and a cross-connector spanning the lateral width of the inside surface of the cap between the openings, the cross-connector having a lower generally semi-cylindrical concave surface for engaging the rod and an upper surface;

a set screw having a head with a wrench engaging surface, a threaded shaft adapted to be threadably received in the threaded surface of the upper section housing and a free end for engaging the upper surface of the cross-connector of the cap to secure the rod between the cross-connector and the screw head so that the rod is held in a fixed position relative to the head of the screw, and

a washer disposed between the cross-connector of the cap and the head of the screw, the washer having a generally concave spherical lower surface and a saddle-shaped upper surface.

5. A pedicle screw assembly for use in conjunction with a rod for immobilizing bone segments comprising:

a screw having a cylindrical threaded shaft and a head having a larger diameter than the shaft with a generally spherically convex bottom section joined to the shaft and a top section defining a wrench engaging surface so that the screw may be rotatably inserted into a bone segment;

a polyaxial housing having an upper and a lower section with an axial passageway therethrough, the passageway in the lower section being larger than the diameter of the threaded shaft of the screw and smaller than the diameter of the screw head, the passageway in the upper section of the housing being larger than the diameter of the head of the screw, whereby the cylindrical shaft of the screw may pass through the housing while the head is retained within the housing, the upper section of the housing defining at least two spaced arcuate upstanding posts with a threaded inside surface, the posts defining a slot therebetween for receiving the rod;

a cup-shaped cap adapted to be inserted over the top section of the housing, the cap having a bottom defining spaced openings for receiving the posts and a cross-connector having a lower surface adapted to engage the rod;

means for threadably engaging the inside surface of the upstanding posts to capture the rod between the housing and the head of the screw; and

a washer positioned between the head of the screw and the rod, the washer having a lower generally concave spherical surface for engaging the screw head and an upper U-shaped surface for engaging the rod.